Centre for Sustainability (CSAFE), University of Otago, Dunedin, New Zealand.
Te Pūnaha Matatini Centre of Research Excellence in Complex Systems, University of Auckland, Auckland, New Zealand.
J Anim Ecol. 2023 Feb;92(2):273-284. doi: 10.1111/1365-2656.13742. Epub 2022 May 23.
When ecosystems are under severe pressure or environments change, trophic position and intraspecific niche width may decrease or narrow, signalling that conservation action is required. In New Zealand, alpine and subalpine ecosystems have been extensively modified through farming since 19th-century European settlement, with consequences for indigenous species such as the kea Nestor notabilis. We investigated feather stable isotope values in the kea and predicted a lower trophic position in modern kea populations, to reflect reduced lowland habitat and a mixed diet with more plant material. We predicted that size and sex would influence trophic values in this sexually dimorphic species, with larger birds more likely to have a high protein diet. We examined potential dietary changes in 68 museum collected kea from 1880s to 2000s, first recording accession details including provenance and sex and measuring culmen length. We used bulk carbon and nitrogen stable isotope analyses (BSIAs) of feathers and a further feather subset using compound-specific stable isotope analyses of amino acids (CSIA-AA) to obtain isotopic values and estimate trophic position. BSIA showed δ N values in kea feathers declined through time and could indicate that early century kea were highly omnivorous, with δ N values on average higher than in modern kea. Variance in δ N values was greater after 1950, driven by a few individuals. Few differences between males and females were evident, although females in the south region had lower δ N values. There was a tendency for large male birds to have higher trophic values, perhaps reflecting dominant male bird behaviour noted in historical records. Nonetheless, CSIA-AA performed on a subset of the data suggested that variation in BSIA is likely due to baseline changes rather than relative trophic position which may be more homogenous than these data indicate. Although there was more variability in modern kea, we suggest caution in interpretation. Stable isotope data, particularly CSIA-AA, from museum specimens can reveal potential change in ecological networks as well as sexually dimorphic feeding patterns within species. The data can reveal temporal and regional variation in species trophic position and changes in ecosystem integrity to inform conservation decision-making.
当生态系统受到严重压力或环境发生变化时，营养级和种内生态位宽度可能会缩小或变窄，这表明需要采取保护行动。自 19 世纪欧洲人定居以来，新西兰的高山和亚高山生态系统已经通过农业得到了广泛的改造，这对本土物种如啄羊鹦鹉（Nestor notabilis）产生了影响。我们研究了啄羊鹦鹉的羽毛稳定同位素值，并预测现代啄羊鹦鹉种群的营养级较低，以反映低地栖息地的减少和以更多植物材料为主的混合饮食。我们预测，在这种性二态物种中，体型和性别会影响营养值，体型较大的鸟类更有可能摄入高蛋白饮食。我们研究了 1880 年代至 2000 年代 68 只博物馆收藏的啄羊鹦鹉的潜在饮食变化，首先记录了包括来源和性别在内的入藏详情，并测量了嘴峰长度。我们使用羽毛的整体碳和氮稳定同位素分析（BSIA）和进一步的羽毛亚组使用氨基酸的化合物特异性稳定同位素分析（CSIA-AA）来获取同位素值并估计营养级。BSIA 显示啄羊鹦鹉羽毛中的 δ N 值随时间而下降，这可能表明早期世纪的啄羊鹦鹉高度杂食，其 δ N 值平均高于现代啄羊鹦鹉。1950 年后，由于少数个体，δ N 值的方差更大。雄性和雌性之间几乎没有明显差异，尽管南部地区的雌性 δ N 值较低。大型雄性鸟类的营养级值较高，这可能反映了历史记录中记录的优势雄性鸟类行为。尽管现代啄羊鹦鹉的变异更大，但我们建议谨慎解释。从博物馆标本中获取的稳定同位素数据，特别是 CSIA-AA，可以揭示生态网络中的潜在变化，以及物种内部的性二态喂养模式。这些数据可以揭示物种营养级的时间和区域变化以及生态系统完整性的变化，为保护决策提供信息。
